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Nanodesigning of multifunctional ceramic composites with colloids is discussed from a fundamental point of view. We start with one-component systems, where packing density is the primary concern. Then we extend the discussion to binary systems and deal with the problem of homogeneity. We show that the structure is controlled by the nature of bonding between the particles and by the particle-particle interaction. Surfactants are used to modiy these properties, by, first, protecting the active particle surfaces to prevent solid bond formation, and, second, altering the interparticle interaction to provide a “lubricating” effect. In weakly attractive multicomponent systems, not only are we able to achieve high-density packing through restructuring, but we can also control the scale of homogeneity.

This paper starts by discussing the concept of multifunctional materials. Multifunctionality can be achieved in a single phase in a composite or a mixture. While a few exceptional single phase materials such as diamond, Al2O3, CaSrZr4P6O24 exhibit peak values of more than one function, it will be argued that the “invention” of the nanocomposite class of materials made by solution sol-gel processing has opened up the potential for designing several multifunctional materials.

Examples will be drawn from our recent results—both successes and failures—in trying to design and synthesize nanocomposites of two or more ceramic phases for various chemical, thermal, and electrical functions.

The sol-gel chemical processing method of producing fully dense silica optics provides an intermediate product termed Type VI silica ideally suited for use in engineering multifunctional silica optics. This paper reviews the sol-gel process, the Type V dense gel-silica produced by this process and the Type VI ultraporous gel-silica intermediate product. Included is a comparison of two different porous ultrastructures with 1.2 nm and 8.0 nm average pore radii. Two uses of the porous gel-silica components as multifunctional optics are described. The first is for use in transpiration cooled windows in highspeed rocket guidance systems. Flow rates of He and N2 through the 1.2 nm and 8.0 nm ultrastructures are as high as 0.9 m/min at 0.75 MPa. High temperature UV transmission in contact with an impinging oxy-acetylene flame is demonstrated. Use of Type VI gel-silica as a host matrix for fast radiationhard scintillating detectors is also reviewed.

UV-VIS spectral comparison with model compounds and isolation of the major product from preparative photolysis of one of the models has been used to show that the predominant photochemical reactions in the solid state of an aryl cinnamate polymer are 2+2 cycloaddition and photo-Fries rearrangement.

Recent developments in the application of electro-optic polymer materials to perform multi-functional roles in integrated optic device applications are summarized and future requirements for practical field operation are discussed.

Synthetic efforts toward novel NLO and piezoelectric polymers are described. NLO-phores are incorporated in the main chain of a polymer with all the dipoles in the same direction by polycondensation of AB-monomers. The polymers containing p-alkoxy-α-cyanocinnamate units in the backbone show cooperative enhancement of SHG in solution. For comparison, p-thio-α-cyanocinnamate is incorporated in the main chain and in the side chain of polymers. Novel potentially piezoelectric polymers synthesized include polymers containing multicyanocyclobutyl or -cyclopropyl groups and acrylonitrile copolymers.

Polymer electrolytes are attracting interest because of potential use in ‘solid state’ batteries and electrochromic windows. In this work the nature of the chemical bonds and ion association in polymer-salt complexes were studied. The fundamental vibrational frequencies of LiClO4− were calculated using valence force constants which are obtained from the ClO4− anion. The calculated frequencies and the band assignments agree quite well with the observed frequencies. Raman and IR spectroscopy were used to investigate the interaction of Li+ and ClO4− with the PEO chains. Lithium ion interacted with the negatively charged oxygen of PEO and C104 interacted electro- statically with the positively charged hydrogens. The strong electrostatic interactions induced changes in the intensity of the Raman bands and IR absorption bands of the polymer. The Raman and IR spectra of the polymer-salt complexes clearly show the existence of ‘free’ ions, ionpairs and salt clusters at various concentrations of the lithium salt. The maximum concentration of “free” ions deduced from the spectroscopy is in excellent agreement with the salt concentration required to obtain maximum ionic conductivity.

A biomedical material for use as artificial bone and dental root is provided which takes the form of a sintered composite body comprising a Hydroxyapatite(HAP) and diopside whisker. The mixed powder of HAP and diopside was heated to make this composite material. The sintering of HAP and the precipitation of diopside whisker were examined, to find a method of making them occur simultaneously. Also, diopside was added to HAP and sintering at 1200°C for 2hr. was done. As a result of these investigations, diopside whisker of aspect ratio 101˜15 was formed. Moreover the intermediate layer of CaO-SiO2-P2O5-MgO system was generated at the interface of HAP and whisker. The bending strength of this sintered body was 300MPa and fracture toughness was 3.2MPa ·m1/2. These values were higher by about 2times or 3times than those of matrix HAP respectively. The increase in bending strength was attributed to an increase in fracture toughness, caused by an increase in fracture surface energy.

Molecular units in natural systems are multifunctional in that they exhibit more than one functionalities. This is nature's way of economizing and being efficient. For many technological applications, there is a need for synthetic multifunctional materials which simultaneously exhibit many necessary physical and chemical properties. By appropriate modification of structures both at the molecular and bulk levels, one can incorporate such multifunctionality in molecular and polymeric systems. Our research program focuses on investigations of multifunctional materials for applications in photonics. Photonics describes the emerging new technology in which a photon instead of an electron is used to acquire, process, store and transmit information.

The third order optical susceptibilities (−3ω; ω, ω ω,) for soluble metallophthalocyanine derivatives were determined by optical third harmonic generation measurements of molecularly doped polymer films at a wavelength of 1907nm. The X(3) value of tetra-tert-butylvanadylphthalocyanine is larger than that of metal-free derivative. We demonstrate experiment on modes of propagating light wave in molecularly doped films which exhibit excellent optical quality. The enhancement of third order optical nonlinear susceptibilities in phthalocyanine compounds are discussed in terms of molecular structure and molecular packing.

Physical properties intrinsic to linear inorganic polymer systems can be modified through replacement of chemical groups external to the chain backbone. This substitution also perturbs chemical bonding along the chain which can further influence polymer properties. Several phosphazene polymers deposited as thin dielectric films exhibit extended ultraviolet transmission. Second harmonic generation (SHG) has been observed in these polymers as well as in cyclic polymer precursors. The relative magnitude of SHG is found to correlate both with the nature of the substitutional group and molecular conformation. Influence of these parameters on substrate-film adhesion and measured optical properties is discussed in terms of substitutional group electronegativity, and electronic charge localization in the polymer chain which is probed using molecular spectroscopic techniques.

New approaches to both second-order and third-order nonlinear optical materials are presented. A series of organometallic and organic salts, in which the cation has been designed to have a large molecular hyperpolarizability, has been prepared and the SHG efficiencies were measured. Partially substituted derivatives of polyacetylene are synthesized via the ring-opening metathesis polymerization (ROMP) of cyclooctatetraene (COT) and its derivatives. Certain poly-COT derivatives afford soluble, highly conjugated polyacetylenes. These materials exhibit large third-order optical nonlinearities and low scattering losses.

Third-order optical nonlinearity in organic materials has generally been sought from molecules and polymers having extended i-electron delocalization in conjugated bonding schemes. In an alternative approach, we have investigated the third-order optical response of a polymeric composite containing charge transfer complexes in which the nonlinearity originates from intermolecular electron delocalization between π-electron clouds in charge transfer stacks. The material, which is composed of a polymer having electrondonating pendant side groups that complex with dopant electron-acceptor molecules, has been processed into an optically clear thin film. Nonlinear characterization of the film by means of third-harmonic generation suggests enhancement of the third-order response arising from charge transfer interactions.

Recent work aimed at developing new polymers which exhibit useful optical, electro-optical, and piezoelectric properties is presented. The materials under study are polymers with methacrylate backbones and oxynitrostilbene side chains. The synthesis is outlined, and pyro-electric, electro-optic, and thermal property data are reported and discussed.

Second order molecular susceptibilities β of poly(γ – benzyl L–glutamate)(PBLG) and poly(γ – p–nitrobenzyl L–glutamate) (PNBLG) were determined by means of dc-induced second harmonic generation (dc-SHG technique in solutions at a wavelength of 1064nm as 1.5×10–−29 esu and −4.9×10−29 esu, respectively. Among PBLG, PNBLG and nitrobenzene, it was found that only PNBLG has negative value of β. It follows that the effect of nitrophenyl groups in side chains is dominant for β whereas the contribution of carbonyl groups in main chain is dominant for the permanent dipole moment μ in PNBLG.

Multifunctional macromolecules can, in principal, combine a number of active material functions such as optical nonlinearity and photoconductivity in one material. Multifunctionality may offer new options for device fabrication and implementation. However, in practice the implementation of a device which uses a range of material properties such as piezoelectricity and photoconductivity in a single layer of active material is some distance away. This is in part due to the difficulty of optimising a material simultaneously for two separate properties. Therefore the approach we have taken is to identify device configurations which rely on multilayers, each separate layer providing one of the active device functions. Initial results on the fabrication and characterisation of two such proof of principle devices, a light modulated deformable mirror and a light modulated electro-optic layer, are described.

Multifunctional engineering systems made up of different material components each providing primarily a single function are well known. Frequently, even for a monofunctional application, the material component must already have an optimum set of secondary properties to fulfill that function. It would be desirable to have multifunctional material components. In this paper some known multifunctional ceramic materials, mainly crystalline and glassy oxide systems, are reviewed. These are conveniently divided into molecular, ultrastructural and integrated materials systems. Projections are made regarding the future developments of multifunctional ceramics as well as nanocomposites with both inorganic and organic components based on the sol-gel technique.

As trends towards miniaturized components and systems continue in many fields, there has been a rapid development in similarly scaled-down composites. In the electronics industry, these nanocomposites (and especially active nanocomposites based on ferroic elements) form a basis for many of the recent advances in both information and charge storage. While the overall properties of some of these composites can be explained as straightforward extrapolations from the bulk properties, in other instances the small size of the ferroic phase has important consequences on the macroscopic behavior of the composite. This paper reviews some of the recent developments in small-scale ferroic nanocomposites and details the relation between component size and the resultant properties.

2-ethylhexanoic acid (2EHA) has been applied to control the YBa2Cu3O7−x sol-gel solution. The experimental results prove that 2EHA functions as a sol-gel solution structure controlling and precipitation-prevention agent. The structure of the solution can be one, two or three dimensions of the network by using different concentration of 2EHA to modify the metal alkoxides. With decreasing 2EHA concentration, the homogeneity is improved due to increasing the network connectivity. This results in: (1) ease of the formation of YBa2Cu3O7−x; (2) denser microstructure with fine grains; and (3) narrower but lower superconducting transition.

New organic/inorganic hybrid materials were prepared by hydrolysis and co-condensation of tetramethylorthosilicate (TMOS) with trimethoxysilane functionalized polyimide oligomers via sol-gel ultrastructure processing. In the first reaction step, amine terminated, fully imidized, soluble, high Tg polyimides were prepared from appropriate diamines and dianhydrides by solution imidization techniques. The amine end-groups were then quantitativell derivatized to nadimide structures through reaction with cis-norbornene 2,3 dicarboxylic anhydride. Subsequently, the nadimides were quantitatively derivatized to trimethoxysilane functionalities via hydrosilylation reactions in the presence of chloroplatinic acid catalyst. The resulting hexamethoxy functionalized polyimide oligomers were hydrolyzed and co-condensed at elevated temperatures under mild pressure with TMOS via sol-gel processing to generate thermally stable polyimidesilicate hybrids. The synthesis and characterization of these materials is discussed.